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NH] UH ILMOHU UNITED STATES PATENT ()FFICE.

SPECIFICATION forming part of Letters Application filed March l, 1883: TFO specimens.)

To all whom it may oncern:

Be it known that I, EDWARD J. DE SMEDT, of the city of Washington, District of Columbia, have invented a new and useful Improvement in the Manufactureof Portland Cement, of which the following is a specification.

Argillo-niagnesian and argillo-calcareous cement-rocks and hydraulic limcstones are louud quite abundantly both in this country and in Enr0pe,and have been used extensively for the manufacture of cement; but although containing silica, alumina, magnesia, and lime and other ingredients they are ineffective in themselves to produce Portland cement, the cement made from them being common cement-- such, for instance, as the cements known in the market as Cumberland cement, ltosendale cement/K310. It has been my ob jeet to devise some way of utilizing these rocks for the manufacture of Portland cement; and l have found that this result can be attained by combining with them dolomite, by which term I intend and mean argillomagnesian limestones containing at least fifteen percent. ofcarbonate ofmagnesia, in suflicient quantity to bring the percentage of lime and magnesia in the compound up to about seventy per cent.

()nc wayin which I carry myinvention into practical effect is as follows: 1 take the com-- cut-rocks or the hvdraulic limestones, or th, and grind them up raw. I ascertain by analysisthechemicalcompositionottheground mass, with a view to determine the extent to which it is deficient in lime or lime and magnesia. I then add to the mass dolomite in such proportion as to make the unmet] Portland cement analyze about seventy per cent. (or, say, from fifty-live or sixty to seventy percent.) of lime and magnesia. After the addition and incorporation of the dolomite the. powdered or ground mass is moistened, made into bricks or other forms, dried, calg ipgd toa clinkcr, and ground into cement undFr'eitlicr the wet process or the dry process, as preferred or, if desired, it may be made into cement in accordance with the process described in my Letters Patent hearing date of March 20, 1853, the characteristic of said patented process residing in the mixture with the cemeutpaste, before calcination, of a hydrocarbon or other combustible.

MANUFACTURE OF PORTLAND CEMENT.

Patent No. 274,735, dated March 27, 1,851

l I can also make, and have also made, Portland cement from ordinary natural cementsuch as Rosendale cement an um er and cementya mg 0 cm dolomite in the proportion hereinbefore indicated, and then moistening the mass, making it into bricks or other forms, recalcining the same to clinker, and then grifiding thecalcined product.

I have also made Portland cement from these ordinary natural cements by first recalcining the latter to chnlIer, and then regrmd- ,ing and adding calcined and ground dolomite in theproportlon hereinbeloreindicate e Portland cement thus obtained is, however, more slow-setting than that obtained by adding dolomite to the mass before calcination.

include within the terms of my claim all of the foregoing-recited methods of applying and using cement-rocks or hydraulic limestoues, whether raw or in the conditions of cements, for the purpose of producing a. Portland cemcut.

Having now described my inventioirand the best way known to me of carrying the same into practical effect, I state my claims as follows:

1-. The improvement in the art of manufac turing Portland cement, consisting in comstones, either before or after the calcining operation, dolomite in substantially the proportions stated. 2. The process of manufacturing Portlan cement, consisting in combining with ground I desire it to be understood that I intend to Dining with cement-rocks or hydraulic limeor pulverized cement-rocks or hydraulic limostones dolomite, in substantially the proportions stated, and subsequently calcining and grinding said compound,substantiallyas here inbefore set forth.

my hand. D

E. J. DE SMEDT. Witnesses J. WALTER BLANDFORD H. B. ZEVELY.

3. The hereinbefore'described product ob-- 

